On Wed, 26 Sep 2001 15:10:35 +0200 "Christian Lox" <lox@xxxxxxxxxxx> wrote: > Hi everyone! > > Sorry if this is a FAQ but I did not find a searchable archive. > > What I am planning to do: > 2 different connections to 2 different ISPs. > One is handled by an ISDN card, one via ethernet to their router > (DSL). > We want to use the DSL line; only if this fails we need the ISDN > line. > I played around with the metrics but could not get it to work. I'm trying to find a solution for this very situation since a long time, but wasn't able to do so. What is working for me now is a small daemon I wrote which essentially replaces ipup and ipdown. Initially it reads the standard /etc/network/interfaces files, paying attention to an additional parameter of priority which is commented out. Then, the interfaces are set up the normal way, but the routes are set with mask /32 just to reach the gateway and no default route. Then, every 60 seconds, a single ping is sent to the gateway of each of the external interfaces, marking it either up or down. After that, the priority value is checked and the program chooses that with the highest priority. If that is also marked active, nothing else is done, but if it wasn't active, the default route is put to that interface and the firewall script is reinitialized. Of course, if the active interface becomes down, the default route is removed. This works fine, but it's a real pitty that I can't use both interfaces in a balanced way as this would effectively duplicate my bandwidth while both are up. Another (small) problem with this approach is, that switching interfaces automatically stops operators from realizing that a line is not working for to take corrective action. So I decided to send an email in such case, which of course fails if both interfaces are down because I'm geografically far from these networks. But then, operators do realize that something is wrong. I wrote this program some days ago and it's really a dirty hack, so I doubt the code would be more useful than this description. I don't have experience with Cisco routers, but was told that load balancing to two or more independent external links is possible with them. So I guess, somehow it should also be possible with Linux. If somebody could shed light on this, I would be really greatful. -- Christoph Simon datageo@xxxxxxxxxxxx --- ^X^C q quit :q ^C end x exit ZZ ^D ? help NO CARRIER .
